1. Field of the Invention
This invention relates to rivets, particularly to the pull-type blind rivets, and a method and means for installing them.
Blind rivets in general find useful application in the riveting of lapped workpieces where access may be conviently had by a worker to one side only. In the trade, the accessible side of the work is often referred to as the "top side" and the opposite side as the "blind side", and for convience these terms are used herein.
Most pull-type blind rivets include two basic parts, namely, a sleeve having a shank and a radially enlarged head, and a pin having a pulling section and a stem, the stem having a head to engage that end of the sleeve remote from the sleeve head. When assembled prior to use, the stem of the pin is received within the sleeve with its pulling section projecting therefrom beyond the rivet sleeve head and with the pin head engaging the sleeve end. Setting of the rivet, as suggested by the class designation, is achieved by pulling the pin head against the end of the sleeve outwardly away from the top side of the work.
In conventional use, an assembled pull type blind rivet is inserted from the top side into substantially aligned apertures in the workpieces. The head of the sleeve is positioned flush with the top side of the work, causing the shank to project on the blind side. An outward pulling force is then applied to the projecting pulling section of the pin and a reactive or restraining force is applied to the head of the sleeve via the head of the pin in order to set the rivet. This causes the portion of the rivet sleeve shank projecting on the blind side to be radially expanded or "upset" progressively to clinch or clamp the workpieces together. As will be understood, when the rivet is fully set, the workpieces are clamped between the sleeve head on the top side and the radially expanded portion of the shank, or blind head as it is known in the art, on the blind side.
2. Description of the Prior Art
In order to leave a final riveted connection, which is relatively flush with the exposed top side of the work, without having to trim the pin in a separate operation, it has heretofore been conventional in the art to provide a pin with a weakened section termed a "breakneck" groove. A number of these had to be provided in order to take care of workpieces having varying thickness. After the shank is upset in the manner described above, resistance to pin travel, and thus tension in the pin, increases under the continued application of the pulling force. The pin, in prior arrangements, was designed to fracture at the appropriate breakneck groove when this tension reaced a predetermined level, whereupon the pulling section of the pin separated from the portion disposed within the sleeve.
It is apparent from the above that in these prior practices it was necessary to cause the stem to be weakened (the provision of the breakneck groove) prior to assembly with the sleeve. United States Patent No. 3,230,818 discloses much of the prior art concept and practice discussed above. A search of the United States patent art was conducted in connection with this invention and a number of references were developed as listed below. No assertion is made, however, that the best patent art was developed although that indeed was the intent of the search. The developed references are: U.S. Pat. Nos. 2,384,037 -- KUGLER, 2,438,201 -- BUCHET, 2,457,417 -- TRAUTMANN, 2,999,610 -- GAPP, 3,017,052 -- KOLEC, 3,055,528 -- SEIFERT, 3,122,948 -- BAUGH, et al., 3,157,305 -- BAUGH, 3,196,662 -- SIMMONS, 3,230,818 -- SIEBOL, 3,638,472 -- ORLOFF, et al., 3,667,340 -- BLACK, et al., 3,698,231 -- DAVIS, JR., Italian Pat. No. 371,817 -- MUSSO.
Of the foregoing patents, the following are generally illustrative of a practice which has long been employed in the art to eliminate excess pin stem, namely, providing some sort of "break-neck" which will rupture when a certain pulling pressure has been reached: U.S. Pat. Nos. 2,384,037; 3,017,052; 3,055,528; 3,122,948; 3,157,305; and 3,196,662. (U.S. Pat. Nos. 3,638,472 and 3,667,340 appear to be of general interest only).
Siebol Patent 3,230,818, earlier discussed, is of importance in that although it does not disclose a means for clipping off or trimming the pin stem, it does disclose a means which causes a crown provided on the outside of the sleeve head to be "buckled" into aligned grooves on the pin stem, see FIGS. 6, 7 and 9. Siebol, however, relied on break-neck grooves for removing the excess pin stem.
Buchet U.S. Pat. No. 2,438,201 discloses means for shearing off the surplus mandrel, note particularly column 2, lines 22 to 30 and column 3, lines 24 to 32.
Trautmann U.S. Pat. No. 2,457,417 refers to the invention as comprising a "stem trimmer". The specifics for accomplishing this, however, differ considerably.
Gapp U.S. Pat. No. 2,999,610 also seems to contemplate some form of "pin trimming", see particularly column 1, lines 57 to 62; column 4, lines 62 to 73; and column 5, lines 1 to 8.
Davis U.S. Pat. No. 3,698,231 also refers to the severing of a lock bolt at a point adjacent the collar by what appears to be a combined swedging and cutting action.